1. Field of the Invention
The present invention relates generally to means for isolating an alternating current (AC) actuated device from a logic control device integrated therewith, combined with means for detecting when the AC actuated device is operational.
2. Description of the Related Art
Many AC devices which perform work are now controlled by digital logic devices such as microcontrollers, microprocessors, or programmable logic controllers (PLCs). Examples of this in the consumer field include numerous household appliances. In the industrial field, a common example would be in material handling operations where various sensors, motors, relays, solenoids, et al. are required to run the conveying and handling apparatus and may be controlled by one or more bus systems, programmable logic controllers, or on board microprocessors. In this instance, it is often critical that immediate detection of a fault condition in an actuated device is available to the operator in order to prevent mishandling, backups, crashes, etc; of the items on the conveyor line.
Further, because digital logic control is incompatible with the AC power required for the actuated devices, isolation between DC logic power and AC device power is highly desirable.
It is further highly desirable that an actuation sensor be accomplished inexpensively and reliably within a small package which can easily be added to or integrated within existing systems.
The present invention provides a means for isolating an AC actuated device and detecting its actuation via a digital controller which controls the actuation. The means generally comprises a circuit having an optocoupler or other suitable means for isolating an AC actuated device, or load, from a DC microcontroller or PLC; a diode network allowing current flow in first and second directions and for biassing the light emitter of the optocoupler; a device actuation switch between the device and the diode network which is controlled by the PLC and; resistor-capacitor (RC) RC charge and discharge paths connected between the phototransistor output of the optocoupler and the PLC to vary the state of an indicator output connection which the PLC can sense to determine that the load is present, i.e. the device is actuated when the device actuation switch is placed in the ON state.
The invention may further comprise suitable biassing and limiting resistors, connection points, DC power supplies and the like as necessary or desirable.